Alberta

[Bernardo de La Paz]

https://kings-printer.alberta.ca/1266.cfm?page=2002_304.cfm&leg_type=Regs&isbncln=9780779856923&display=html

Part 1 Division 1 Section 2 (1)(b) says in the left lane you must drive at or near the speed limit, except for (because subject to this Part including):

(1)(c) which says a person shall not " (c) drive a vehicle at such a slow rate of speed so as to impede or block the normal and reasonable movement of traffic then existing on a highway except when it is necessary to do so for the safe operation of the vehicle"

Section 2(1)(c) means that you can't impede traffic in the left lane by going at the speed limit when existing traffic is moving faster and it means you can't enforce speed limits by driving in the left at the speed limit.

(2) says despite (1)(b) "a person driving a vehicle on a highway at a speed that is below the maximum speed limit that is established or prescribed for that highway may drive the vehicle in the traffic lane nearest to the centre line for the purpose of overtaking and passing another vehicle."

So by (2) you can pass another vehicle at slower than the limit.

3(1) If a person driving a vehicle is driving the vehicle on a highway at a speed that is less than the normal speed of the traffic on the highway at that time and place and under the conditions then existing, that person shall drive the vehicle
(a) in the right traffic lane then available for traffic,

Section 3(1) means the speed at that time and place then existing (normal at that time and place). So if the traffic is flowing faster than the speed limit you have to drive in the right lane to get out of its way.